KR19980071202A - Oxygen Absorption Storage Cerium Composite Oxide - Google Patents

Abstract

It provides a cerium-based composite oxide having a high oxygen storage function (OSC) and capable of maintaining a high oxygen storage function even under severe conditions, for example, at a high temperature of 800 ° C or higher.

Ce _{1- (x + y)} Zr _x R _y O _2-z is a cerium-based composite oxide,

R represents a rare earth metal and is 0.2≤x + y≤0.9, 0.1≤x≤0.8, 0.05≤y≤0.3, preferably 0.4≤x + y≤0.8, 0.35≤x≤0.7, 0.05≤y≤0.2 It is characterized by that.

Description

Oxygen Absorption Storage Cerium Composite Oxide

The present invention is an oxygen absorption storage cerium used to efficiently operate a catalyst for purifying nitrogen oxides (NO _X ), carbon monoxide (CO) and hydrocarbons (HC) contained in exhaust gases emitted from internal combustion engines such as automobiles. It relates to a system complex oxide.

Exhaust gases emitted from internal combustion engines, such as automobiles, contain harmful substances such as NO _X , CO, and HC, and regulations on the purification of these hazardous substances are becoming more stringent from the viewpoint of protecting the environment. On the other hand, in terms of fuel economy, the fuel lean state (hereinafter referred to as the "stake state") is less than the mixer state of the theoretical performance ratio (hereinafter referred to as the "stalk state") in normal driving except when the vehicle is idled and accelerated. Control to operate the internal combustion engine in a "lean" state has been widely practiced. Therefore, there is a strong demand for the development of a catalyst capable of effectively purifying the above toxic substances not only in the stock state but also in such a lean state.

As the most widely used catalyst for purifying the harmful substances from the exhaust gas, there is a so-called three-way catalyst using noble metals such as platinum, palladium and rhodium as active materials. This three-way catalyst acts as a catalyst for the reduction reaction from NO _X to N ₂ or the oxidation reaction from CO to CO ₂ and HC to CO ₂ and H ₂ O. In other words, the three-way catalyst may act as a catalyst for both reactions of oxidation and reduction.

Therefore, various studies have been conducted to improve the activity of the three-way catalyst. For example, a function of absorbing and storing oxygen in the gas phase of cerium oxide (CeO ₂ ) in the crystal or releasing it from the crystal, a so-called oxygen streak. Some have paid attention to OSC. In other words, by adding the cerium oxide to the ternary catalyst, the oxygen concentration of the gaseous atmosphere is prepared. In the O ₂ rich state, the excess oxygen in the gaseous atmosphere is absorbed and stored in the crystal of cerium oxide, and NO _x by the ternary catalyst While promoting the reduction reaction, the oxygen and oxygen rich in the gaseous atmosphere is released from the crystals to improve the oxidation reaction efficiency by the three-way catalyst.

However, there is an increasing demand for changing the mounting position of the catalyst from the bottom of the vehicle body to the manifold position adjacent to the engine so that the catalyst can be quickly warmed and functioning immediately after starting the engine. When the catalyst for exhaust gas purification is mounted close to the engine in this manner, the catalyst may be exposed to a high temperature of 900 ° C. or higher, and under such high temperatures, the cerium oxide granulates (sinters) to decrease the specific surface area. .

Since the cerium oxide granules grow and the specific surface area decreases, the oxygen streaks decrease, so that the above-mentioned three-way catalytic activity cannot be improved.

Therefore, the addition of zirconium, lanthanum, etc. to cerium oxide has been proposed to suppress the growth of granules of cerium oxide (see Japanese Patent Application Laid-Open No. 61-262521, Japanese Patent Application Laid-Open No. 61-262522). Iii) the original properties of cerium oxide were lost, and the mixture was not sufficiently endurable under high temperature.

The present invention has been devised under the above circumstances, and has a high oxygen storage function (OSC) and a cerium system capable of maintaining a high oxygen storage function even under severe conditions, for example, at a high temperature of 900 ° C or higher. It is the subject to provide a composite oxide.

In order to solve the above problems, the present invention is a general formula

Ce _{1- (x + y)} Zr _x R _y O ₂ -z

Is indicated by

R represents a rare earth metal, z represents an oxygen content, and 0.2 ≦ x + y ≦ 0.9, 0.1 ≦ x ≦ 0.8, and 0.05 ≦ y ≦ 0.3. Provided is an oxidation absorption storage cerium-based composite oxide.

Moreover, it is preferable that at least one part of the said cerium complex oxide is a solid solution. More specifically, it is preferable that a part of cerium in the cerium oxide crystal is solid-substituted by zirconium and rare earth metal. It is because zirconium inhibits the mass transfer of cerium oxide and the cerium-based composite oxide is granulated (sintered) and dried, by dissolving cerium in the crystal of cerium oxide by zirconium.

In the cerium-based composite oxide, the atomic ratio of zirconium represented by x is in the range of 0.1 to 0.8 as described above. Zirconium suppresses the diffusion of cation in cerium oxide and prevents the growth of the cerium-based composite oxide at high temperature, but when the atomic ratio of the zirconium is smaller than this range, the growth of the cerium-based composite oxide is prevented. This is because it is difficult to sufficiently suppress it, and when it is larger than the above range, the atomic ratio of cerium itself becomes small, which causes a decrease in the oxygen absorption storage amount.

In this case, in order to obtain a more favorable effect, it is preferable to make x into the range of 0.35 to 0.7. In addition, the zirconium may contain hafnium (Hf), which is usually contained in 1-2% in the ore.

The reason why cerium in the cerium oxide crystal is substituted and employed by the rare earth metal is that the crystal structure of the cerium-based composite oxide can be stabilized in a fluorite-like lattice structure even at room temperature. As described above, the atomic ratio of the rare earth metal in the cerium-based composite oxide is represented by y and is in the range of 0.05 to 0.3.

When the atomic ratio of the rare earth metal is smaller than this range, the cerium-based composite oxide is composed of cerium oxide containing zirconium and zirconium oxide containing cerium due to the difference in the ionic radius between cerium and zirconium. It becomes difficult to separate | separate two layers and to maintain a uniform fluorite-type crystal structure favorably.

In addition, when it is larger than the above-mentioned range, the rare earth metal additionally produces a compound other than the desired composite oxide, or the atomic ratio of cerium and zirconium is relatively small, so that the function of these elements can be sufficiently exhibited. Because there is no concern. In this case, it is preferable to make y into the range of 0.05 to 0.2 in order to acquire a more favorable effect.

In addition, examples of the rare earth metal R include yttrium, scandium, lanthanum, praseodymium, neodymium, promethium, samarium, urobium, gardrinium, terbium, dysprosium, rhodium, erbium, thulium, ytterbium, and ruthetium. (Y) is used. Moreover, these rare earth metals R may be used individually or in combination of 2 or more types.

In addition, the range of 0.2 to 0.9 is most suitable as the range of the atomic ratio x of zirconium in the cerium-based composite oxide and x + y in which the atomic ratio y of the rare earth metal is added. The value obtained by subtracting x + y from 1 is the atomic ratio of cerium in the cerium-based composite oxide.

Therefore, the atomic ratio 1- (x + y) of cerium in the cerium-based composite oxide is in the range of 0.1 to 0.8. The reason why cerium-based composite oxides have an oxygen storage function (OSC) is because cerium is oxidized or reduced, so the number of values changes. Considering this fact, if the atomic ratio of cerium is set too small, oxygen oxide inherent in cerium oxide is inherent. If the atomic ratio of cerium is not sufficiently exhibited and the atomic ratio of cerium is small, the atomic ratio of zirconium or rare earth metal is large. Therefore, when the atomic ratio of zirconium is large, the cerium-based composite oxide is separated into two layers. When the atomic ratio of the rare earth metal is rolled up or large, a defect occurs that additionally produces a compound other than the desired complex oxide. On the contrary, when the atomic ratio of cerium is too large, the atomic ratio of zirconium or rare earth metal is unduly small and cannot fully exhibit the original function of zirconium or rare earth metal. Therefore, as said atomic ratio of cerium, the said range is valid, More preferably, it is 0.2 to 0.6.

Moreover, it is preferable to use a cerium type composite oxide carrying a noble metal or a transition metal. The noble metals or transition metals supported on the cerium-based composite oxides exhibit excellent catalysis for the purification reaction by oxidation and reduction of automobile exhaust gases. It serves to assist the release. In other words, when the noble metal or the transition metal is supported on the cerium-based composite oxide, the time until the cerium-based composite oxide releases a predetermined amount of oxygen and reaches an equilibrium according to the conditions of the gaseous atmosphere can be shortened.

In addition, ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), platinum (Pt) and gold (Au) may be used as the noble metal. Rhodium and palladium are used, and as the transition metal, at least one of a crowd consisting of iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) is preferably selected, and more preferably iron ( Fe) is used. As the method of supporting these noble metals or transition metals on a cerium-based composite oxide, a known method is adopted.

The cerium-based composite oxide of the present invention can be prepared using a well-known method. For example, an aqueous solution is obtained by adding water to a cerium carbonate powder to form a slurry, and then mixing a zirconium salt and a rare earth metal salt in a predetermined stoichiometric ratio to the slurry. After the addition of the mixture, the mixture was sufficiently stirred and then subjected to heat treatment to obtain the cerium-based composite oxide of the present invention.

Although cerium carbonate powder may be any commercially available, it is preferable that the specific surface area is large in order to enhance the oxygen stray function, and that the crystal grain size is 0.1 µm or less is optimal. About 10-50 weight part of water is added to 1 weight part of this cerium carbonate powder, and it is set as a slurry.

As zirconium salt, besides inorganic salts, such as zirconium oxychloride, zirconium oxynitrate, and zirconium oxy sulfate, organic salts, such as zirconium oxy acetate, are mentioned, Preferably zirconium oxynitrate is used. Examples of the rare earth metal salts include inorganic salts such as sulfates, nitrates, hydrochlorides, and phosphates, organic salts such as acetates and oxalates, and are preferably used for nitrates. These zirconium salts and rare earth metal salts are dissolved in 0.1 to 10 parts by weight of water with respect to 1 part by weight, respectively, at a ratio that falls within the predetermined atomic ratio range in terms of stoichiometric ratio to obtain a mixed aqueous solution.

This mixed aqueous solution is added to the slurry and sufficiently stirred and mixed, followed by heat treatment. This heat treatment is first carried out under reduced pressure drying using a vacuum dryer or the like, and then preferably dried at about 50 ° C. to 200 ° C. for about 1 to 48 hours to obtain a dried product, and the resulting dried product is about 350 ° C. to 1000 ° C., preferably It is performed by baking at about 400 to 700 degreeC for about 1 to 12 hours, preferably about 2 to 4 hours. In this firing, preferably, at least a part of the composite oxide is made into a solid solution to increase the heat resistance of the composite oxide. Suitable firing conditions for forming a solid solution are appropriately determined by the composition and proportion thereof of the cerium-based composite oxide.

In the cerium-based composite oxide of the present invention, a solution of a salt containing cerium, zirconium and rare earth metals is prepared to have a predetermined stoichiometric ratio, and an alkaline aqueous solution or an organic acid is added to the solution to contain cerium, zirconium and rare earth metals. After coprecipitating a salt, the coprecipitate is oxidized or a mixed alkoxide solution containing cerium, zirconium and rare earth metals is prepared, and deionized water is added to the mixed alkoxide solution for coprecipitation or hydrolysis. You may heat-treat this co-precipitation or a hydrolysis product.

In this case, as the salt to be used, salts of the above examples as salts of cerium salts, zirconium salts and rare earth metal salts are used. As aqueous alkali solutions, ammonia, anmonium carbonate, and the like are used, and as the organic acid, hydroxide, citric acid and the like are used.

On the other hand, as the alkoxide of the mixed alkoxide solution, methoxide, ethoxide, propoxide, butoxide of cerium, zirconium and rare earth metals, ethylene oxide adducts thereof and the like are used.

In addition, when heat-treating the obtained coprecipitate or hydrolyzate, these coprecipitates or hydrolyzate are dried by filtration and washing, preferably at about 50 ° C to 200 ° C for about 1 to 48 hours to obtain a dried product. Is fired at about 350 ° C to 1000 ° C, preferably 400 ° C to 700 ° C for about 1 to 12 hours, preferably about 2 to 4 hours. In this firing, preferably, at least a part of the composite oxide becomes a solid solution to increase the oxidation resistance of the composite oxide. Suitable firing conditions are appropriately determined by the composition of the composite oxide and its ratio.

The cerium-based composite oxide of the present invention thus obtained is further improved in efficiency by supporting a noble metal and / or a transition metal.

As said precious metal, the platinum group element which consists of ruthenium, rhodium, palladium, osmium, iridium, and platinum as mentioned above is mentioned, Preferably, rhodium and palladium are used.

As said transition element, Fe, Co, Ni, Cu, etc. are mentioned preferably.

The method of supporting the noble metal or transition element on the composite oxide may be any known method, for example, by preparing a solution of a salt containing the noble metal or transition element and impregnating the salt solution with the composite oxide. In this case, as the salt solution, a solution of any of the salts in the above examples may be used, and in practice, a nitrate aqueous solution, dinitrodianmine nitrate solution, chloride aqueous solution, or the like is used.

The salt-containing solution contains about 1 to 20% by weight of a noble metal salt or a transition metal salt, and after impregnating the composite oxide, is preferably dried at about 50 ° C to 200 ° C for about 1 to 48 hours and then about 350 ° C to It is performed by baking at 1000 degreeC for about 1 to 12 hours, and carrying out.

As another method, a solution of a salt containing a precious metal or a transition element is added when coprecipitation or hydrolysis of a solution of a salt containing cerium, zirconium and a rare earth metal or a mixed alkoxide solution in the process for producing a composite oxide. And a method of coprecipitating a noble metal or a transition element with each component of the composite oxide and then performing a heat treatment. As a solution of the noble metal salt used in this case, the salt-containing solution of the above description, such as a nitrate aqueous solution, a dinitrodianmine nitrate solution, a chloride solution, etc. are mentioned.

Specifically, palladium nitrate solution, dinitrodianmine palladium nitrate solution, tetravalent palladium anmine nitrate solution, rhodium nitrate solution, rhodium chloride solution, etc. are used as a palladium salt solution. As the solution of the transition element salt, nitrate is preferably used, for example iron nitrate, cobalt nitrate, nickel nitrate, copper nitrate and the like.

Subsequently, the heat treatment of the obtained coprecipitate to be carried out is carried out under reduced pressure drying using a vacuum dryer or the like, and is preferably dried at about 50 ° C to 200 ° C for about 1 to 48 hours to obtain the resulting dried product at about 350 ° C to 1000 ° C. It is performed by baking for about 1 to 12 hours, Preferably it is 400 to 700 degreeC, about 1 to 12 hours, Preferably it is about 2 to 4 hours.

Embodiment of the Invention

Next, the Example of this invention is described with a comparative example.

Example 1

In the present embodiment, the cerium-based composite oxide having a composition of Ce _0.6 Zr _0.30 Y _0.10 O _{1.95 /} 0.5wt% Fe is used for the initial oxygen streak function of the cerium-based composite oxide, and the oxidation under high temperature. By comparing the oxygen staging function after the reduction endurance test (aging), the durability (change rate) under the harsh conditions of the cerium-based composite oxide was evaluated. The results are shown in Table 1. In the composition of the cerium-based composite oxide, the portion expressed by "/0.5wt%Fe" is Fe having a weight equivalent to 0.5 wt% based on the weight of the cerium-based composite oxide containing no Fe (iron). Indicates that it is supported.

(Preparation of Cerium Composite Oxide)

The cerium-based composite oxide of the above composition was prepared by the so-called alkoxide method.

First, 38.4 g (0.102 mol) of cerium isopropoxide, 16.7 g (0.051 mol) of zirconium isopropoxide, and 4.5 g (0.017 mol) of yttrium isopropoxide were dissolved in 200 ml of toluene to prepare a mixed alkoxide solution. . The mixed alkoxide solution was added dropwise in 600 ml of deionized water for about 10 minutes to hydrolyze the alkoxide.

The solvent and H ₂ O were distilled off and evaporated to dryness and solidified from the hydrolyzed solution to prepare a precursor. The precursor was ventilated at 60 ° C. for 24 hours, and then heat-treated at 450 ° C. for 3 hours with an electric furnace. To obtain a powder of cerium-based composite oxide having a composition of Ce _0.6 Zr _0.30 Y _0.10 O _1.95 . 20 ml of deionized water was added to 20.0 g of this oxide powder to obtain a slurry.

In addition, 0.73 g of a ferric nitrate reagent (iron content of 13.8 wt%) was dissolved in 20 ml of deionized water to obtain 1.0 wt% of iron content, added to the slurry, mixed uniformly, and then H ₂ O distilled off and evaporated to dryness. Solidified. The powder thus obtained was ventilated for 24 hours at 60 ° C., and then heat-treated at 450 ° C. for 3 hours with an electric furnace to obtain a cerium-based composite oxide having a composition of Ce _0.6 Zr _0.30 Y _0.10 O _1.95 /0.5 wt% Fe.

(Evaluation of initial oxygen storage function)

About 18 mg of the cerium-based composite oxide powder prepared as described above is taken as a sample, and it is maintained at 500 ° C. for 15 minutes in a 50% oxygen (remaining nitrogen) stream, and then 20% hydrogen (at 500 ° C. again). The balance of nitrogen) and 50% oxygen (balance of nitrogen) were alternately flowed, and the oxidation / reduction was repeated for 3 cycles of 1 cycle of oxidation and reduction, and the oxygen absorption storage release function of the cerium-based composite oxide was measured. The weight of the sample at this time was measured with a heat balance over time and shown in a chart. Based on the oxidation / reduction cycle in which the chart waveform is the safest, the difference between the weight at the end of oxidation and the weight at the end of reduction is calculated, and this value is estimated as the weight of oxygen that the sample can absorb or store or release.

Also, based on the weight of the oxygen and the weight of the sample, the mol number of oxygen that 1 mol of cerium-based composite oxide can absorb or store or release was calculated as the oxygen storage function.

(Redox endurance test)

This redox endurance test (aging) is a test performed to evaluate the durability of cerium-based composite oxides by exposing the cerium-based composite oxides to a gas flow that simply models the actual state of change of vehicle exhaust gas. Specifically, a total of two cycles of four cycles and a sample (finished initial stabilization) are performed for 5 minutes in purge gas (fuge), 10 minutes in oxidizing gas, 5 minutes in purge gas (fuge), and 10 minutes in reducing gas as one cycle. Was maintained in the gas stream.

The inert gas contains 8 vol% CO ₂ and the rest is N ₂ , the oxidizing gas contains 1 vol% O ₂ and 8 vol% CO ₂ and the rest is N ₂ , and the reducing gas is 1.5 Volume% CO and 0.5 volume% H ₂ are contained, and the remainder is N ₂ . In addition, water (water vapor) in an amount corresponding to 10% by volume of the total amount of gas was added to the gas having any of the above compositions. Moreover, the gas of any composition mentioned above set temperature to 1000 degreeC.

(Evaluation of Oxygen Stray Function after Endurance Test)

The oxidation and reduction cycle in which the sample after the above-described redox test was repeated in the oxidation and reduction at 500 ° C. as in the initial evaluation of the oxygen streak function, and the waveform showing the change over time of the weight measured by the heat balance was stable. The difference between the weight at the end of oxidation and the weight at the end of reduction was calculated.

Based on this value, the oxygen storage function after the endurance test was evaluated by the same method as the evaluation of the initial oxygen storage function.

(Evaluation rate of change)

The rate of change in Table 1 is calculated by the following formula.

Equation 1

In other words, the rate of change is an index indicating the deterioration rate of the oxygen storage function of the cerium-based composite oxide after the endurance test for the initial oxygen storage function.

Example 2

The same procedure as in Example 1 was carried out except that the cerium-based composite oxide had a composition of Ce _0.50 Zr _0.375 Y _0.125 O _1.9375 /0.5wt%Fe. The rate of change (deterioration rate) of the oxygen storage function of the cerium-based composite oxide before and after the function evaluation and the endurance test was evaluated. The results at this time are shown in Table 1. The cerium-based composite oxide was prepared in the same manner as in Example 1.

However, cerium isopropoxide, zirconium isopropoxide, and yttrium isopropoxide are mixed in a ratio different from that of Example 1 so that cerium, zirconium and yttrium form a complex oxide in a predetermined stoichiometric ratio in the state of the composite oxide. Ferric nitrate solution dissolved in toluene to prepare a mixed alkoxide solution and contained in a slurry containing Ce _0.50 Zr _0.375 Y _0.125 O _1.9375 powder to contain a predetermined amount of Fe (iron) (iron content is 1.0wt %) Was adjusted.

Example 3

_Oxygen stripes after initial and endurance tests of cerium-based composite oxides were carried out in the same manner as in Example 1, except that cerium-based composite oxides had a composition of Ce _0.40 Zr _0.45 Y _0.15 O _1.925 /0.4wt%Co. Evaluation of the function and the rate of change (deterioration rate) of the oxygen storage function of the cerium-based composite oxide before and after the endurance test were performed. The results at this time are shown in Table 1. In addition, the cerium-based composite oxide was prepared in the same manner as in Example 1.

However, cerium isopropoxide, zirconium isopropoxide, and yttrium isopropoxide are mixed in a ratio different from that of Example 1 so that cerium, zirconium and yttrium form a complex oxide in a predetermined stoichiometric ratio in the state of the composite oxide. First cobalt nitrate solution (cobalt content is mixed with a slurry containing Ce _0.40 Zr _0.45 Y _0.15 O _1.925 powder so as to dissolve in toluene to prepare a mixed alkoxide solution, and to contain a predetermined amount of Co (cobalt). 1.0 wt%).

Example 4

The same procedure as in Example 1 was carried out, except that the cerium-based composite oxide had a composition of Ce _0.20 Zr _0.60 Y _0.20 O _1.90 /0.7wt% Ni, and the initial and endurance test of the cerium-based composite oxide was carried out. Evaluation of the lazy function and the rate of change (deterioration rate) of the oxygen storage function of the cerium-based composite oxide before and after the endurance test were performed. The results at this time are shown in Table 1. In addition, the cerium-based composite oxide was prepared in the same manner as in Example 1.

However, cerium isopropoxide, zirconium isopropoxide, and yttrium isopropoxide are mixed in a ratio different from that of Example 1 so that cerium, zirconium and yttrium form a complex oxide in a predetermined stoichiometric ratio in the state of the composite oxide. Nickel nitrate solution (nickel content is 1.0wt) dissolved in toluene to prepare a mixed alkoxide solution, and mixed in a slurry containing Ce _0.20 Zr _0.60 Y _0.20 O _1.90 powder to contain a predetermined amount of Ni (nickel). %) Was adjusted.

Example 5

The same procedure as in Example 1 was carried out except that the cerium-based composite oxide had a composition of Ce _0.50 Zr _0.375 Y _0.125 O _1.9375 /1.0wt% Cu. Evaluation of the function and the rate of change (deterioration rate) of the oxygen storage function of the cerium-based composite oxide before and after the endurance test were performed. The results at that time are shown in Table 1. In addition, the cerium-based composite oxide was prepared in the same manner as in Example 1.

However, cerium isopropoxide, zirconium isopropoxide, and yttrium isopropoxide are mixed in a ratio different from that of Example 1 so that cerium, zirconium and yttrium form a complex oxide in a predetermined stoichiometric ratio in the state of the composite oxide. Dissolve in toluene to prepare a mixed alkoxide solution, and mix with a slurry containing Ce _0.50 Zr _0.375 Y _0.125 O _1.9375 powder to contain a predetermined amount of Cu (copper) (copper content is 1.0 wt%) was adjusted.

Example 6

The same procedure as in Example 1 was carried out except that the cerium-based composite oxide had a composition of Ce _0.60 Zr _0.30 Y _0.10 O _1.95 /0.1 wt% Rh, and the oxygen streaks after the initial and endurance tests of the cerium-based composite oxide were performed. Evaluation of the function and the rate of change (deterioration rate) of the oxygen storage function of the cerium-based composite oxide before and after the endurance test were performed. The results at this time are shown in Table 1.

In addition, the cerium-based composite oxide was prepared in the same manner as in Example 1. Again, the weight of the rhodium nitrate solution (rhodium content: 0.980 wt%) mixed in the slurry containing Ce _0.60 Zr _0.30 Y _0.10 O _1.95 powder was adjusted so that a predetermined amount of Rh (rhodium) was supported.

Example 7

_Oxygen streaks after initial and endurance tests of cerium-based composite oxides were carried out in the same _{manner as in} Example 1, except that the cerium-based composite oxides had a composition of Ce _0.40 Zr _0.45 Y _0.15 O _1.925 /0.1wt%Rh. Evaluation of the function and the rate of change (deterioration rate) of the oxygen storage function of the cerium-based composite oxide before and after the endurance test were performed. The results at this time are shown in Table 1. In addition, the cerium-based composite oxide was prepared in the same manner as in Example 1.

However, cerium isopropoxide, zirconium isopropoxide, and yttrium isopropoxide are mixed in a ratio different from that of Example 1 so that cerium, zirconium and yttrium form a complex oxide in a predetermined stoichiometric ratio in the state of the composite oxide. Rhodium nitrate solution (rhodium content is 0.980 wt%), which is dissolved in toluene to prepare a mixed alkoxide solution, and mixed in a slurry containing Ce _0.40 Zr _0.45 Y _0.15 O _1.925 powder to carry a predetermined amount of Rh (rhodium). ) Weight was adjusted.

Example 8

The same procedure as in Example 1 was carried out except that the cerium-based composite oxide had a composition of Ce _0.20 Zr _0.60 Y _0.20 O _1.90 /0.05wt% Rh. Evaluation of the lazy function and the rate of change (deterioration rate) of the oxygen storage function of the cerium-based composite oxide before and after the endurance test were performed. The results at this time are shown in Table 1. In addition, the cerium-based composite oxide was prepared in the same manner as in Example 1.

However, cerium isopropoxide, zirconium isopropoxide, and yttrium isopropoxide are mixed in a ratio different from that of Example 1 so that cerium, zirconium and yttrium form a complex oxide in a predetermined stoichiometric ratio in the state of the composite oxide. Rhodium nitrate solution (Rhodium content is 0.980 wt%), which is dissolved in toluene to make a mixed alkoxide solution, and mixed in a slurry containing Ce _0.20 Zr _0.60 Y _0.20 O _1.90 powder so that a predetermined amount of Rh (rhodium) is supported. ) Weight was adjusted.

Example 9

Oxygen storage function after the initial and endurance test of the cerium-based composite oxide was carried out in the same manner as in Example 1, except that the cerium-based composite oxide had a composition of Ce _0.60 Zr _0.30 Y _0.10 O _1.95 /0.1wt%Pd. The change rate (deterioration rate) of the oxygen storage function of the cerium-based composite oxide before and after the endurance test was evaluated. The results at this time are shown in Table 1. In addition, the cerium-based composite oxide was prepared in the same manner as in Example 1.

Furthermore, the weight of the palladium nitrate solution (4.399 wt% of palladium content) mixed in the slurry containing Ce _0.60 Zr _0.30 Y _0.10 O _1.95 powder was adjusted so that a predetermined amount of Pd (palladium) may be supported.

Example 10

_Oxygen streaks of the initial and endurance tests of the cerium-based composite oxides were carried out in the same manner as in Example 1, except that the cerium-based composite oxides had a composition of Ce _0.40 Zr _0.45 Y _0.15 O _1.925 /0.05wt%Pd. Evaluation of the function and the rate of change (deterioration rate) of the oxygen storage function of the cerium-based composite oxide before and after the endurance test were performed. The results at this time are shown in Table 1. In addition, the cerium-based composite oxide was prepared in the same manner as in Example 1.

However, cerium isopropoxide, zirconium isopropoxide, and yttrium isopropoxide are mixed in a ratio different from that of Example 1 so that cerium, zirconium and yttrium form a composite oxide in a predetermined stoichiometric ratio in the state of the composite oxide. _{Dinitrodianminepalladium} nitrate solution (palladium content) which is dissolved in toluene to form a mixed alkoxide solution and mixed in a slurry containing Ce _0.40 Zr _0.45 Y _0.15 O _1.925 powder so as to support a predetermined amount of Pd (palladium). Silver 8.337 wt%).

Example 11

Oxygen streak function after initial and endurance test of cerium-based composite oxides by performing the same operation as in Example 1, except that the cerium-based composite oxides were composed of Ce _0.20 Zr _0.60 Y _0.20 O _1.90 /0.2wt%Pd. The change rate (deterioration rate) of the oxygen storage function of the cerium-based composite oxide before and after the endurance test was evaluated. The results at this time are shown in Table 1. In addition, the cerium-based composite oxide was prepared in the same manner as in Example 1.

However, cerium isopropoxide, zirconium isopropoxide, and yttrium isopropoxide are mixed in a ratio different from that of Example 1 so that cerium, zirconium and yttrium form a complex oxide in a predetermined stoichiometric ratio in the state of the composite oxide. Dinitrodianminepalladium nitrate solution (palladium content is dissolved in toluene to make a mixed alkoxide solution and mixed in a slurry containing Ce _0.20 Zr _0.60 Y _0.20 O _1.90 powder so that a predetermined amount of Pd (palladium) is supported). 8.337 wt%).

Comparative Example 1

Evaluation of oxygen streak function after initial and endurance tests of cerium-based composite oxides, and durability, were carried out in the same manner as in Example 1, except that the cerium-based composite oxides had a composition of Ce _0.60 Zr _0.30 Y _0.10 O _1.95 . The rate of change (deterioration rate) of the oxygen storage function of the cerium-based composite oxide before and after the test was evaluated. The results at this time are shown in Table 1. In addition, the cerium-based composite oxide was prepared in the same manner as in Example 1.

However, cerium isopropoxide, zirconium isopropoxide, and yttrium isopropoxide are mixed in a ratio different from that of Example 1 so that cerium, zirconium and yttrium form a complex oxide in a predetermined stoichiometric ratio in the state of the composite oxide. It was dissolved in toluene to prepare a mixed alkoxide solution.

Comparative Example 2

The same procedure as in Example 1 was carried out except that a cerium-based composite oxide having a composition of CeO ₂ was used, and the above-mentioned before and after the evaluation and evaluation of oxygen storage function after the initial and endurance tests of the cerium-based oxide. The rate of change (deterioration rate) of the oxygen storage function of the cerium-based composite oxide was evaluated. The results at this time are shown in Table 1. In addition, the said cerium oxide was prepared by the alkoxide method similarly to Example 1.

However, since the oxide used in this comparative example does not contain zirconium and yttrium, a cerium alkoxide solution, not a mixed alkoxide solution, is prepared, and the H ₂ O solvent is distilled off and evaporated after the solution is hydrolyzed. Drying solidified to form a precursor, which was prepared by calcining the precursor again.

Comparative Example 3

Oxygen storage function after initial and endurance test of cerium-based composite oxide by performing the same operation as in Example 1 except that Ce-based composite oxide having a composition of Ce _0.6 Zr _0.3 Y _0.1 O _1.95 /0.1wt% Pt was used. The change rate (deterioration rate) of the oxygen storage function of the cerium-based composite oxide before and after the endurance test was evaluated. The results at this time are shown in Table 1. In addition, the cerium-based composite oxide was prepared in the same manner as in Example 1.

However, in the state of the composite oxide, cerium, zirconium and yttrium are mixed to form a mixed alkoxide solution so as to form the composite oxide at a predetermined stoichiometric ratio, and contain Ce _0.6 Zr _0.3 Y _0.1 O _1.95 powder so as to support a predetermined amount of platinum. The weight of the dinitrodianmine platinum nitrate solution (platinum content: 4.569 wt%) mixed in the slurry was adjusted.

Comparative Example 4

Oxygen storage function after initial and endurance test of cerium-based composite oxide by performing the same operation as Example 1 except that Ce-based composite oxide having a composition of Ce _0.40 Zr _0.45 Y _0.15 O _1.925 /0.1wt% Pt was used. The change rate (deterioration rate) of the oxygen storage function of the cerium-based composite oxide before and after the endurance test was evaluated. The results at this time are shown in Table 1. In addition, the cerium-based composite oxide was prepared in the same manner as in Example 1.

However, in the state of the composite oxide, cerium, yttrium and zirconium are prepared to form a mixed alkoxide solution so as to form the composite oxide at a predetermined stoichiometric ratio, and contain Ce _0.40 Zr _0.45 Y _0.15 O _1.925 powder so as to support a predetermined amount of platinum The weight of the dinitrodianmine platinum nitrate solution (platinum content: 4.569 wt%) mixed in the slurry was adjusted.

Comparative Example 5

Oxygen streak function after initial and endurance test of cerium-based composite oxide by the same operation as in Example 1, except that the cerium-based composite oxide had a composition of Ce _0.20 Zr _0.60 Y _0.20 O _1.90 /0.1wt% Pt. The change rate (deterioration rate) of the oxygen storage function of the cerium-based composite oxide before and after the endurance test was evaluated. The results at this time are shown in Table 1. In addition, the cerium-based composite oxide was prepared in the same manner as in Example 1.

However, in the state of the composite oxide, a mixed alkoxide solution is prepared so that cerium, yttrium and zirconium form the composite oxide at a predetermined stoichiometric ratio, and it contains Ce _0.20 Zr _0.60 Y _0.20 O _1.90 powder so as to support a predetermined amount of platinum. The weight of the dinitrodianmine platinum nitrate solution (platinum content is 4.569 wt%) mixed in the slurry to make it adjust.

Furtherance Initial OSC Endurance OSC % Change Example 1 Ce _0.6 Zr _0.3 Y _0.1 O _1.95 /0.5wt% Fe 44 40 9.1 Example 2 Ce _0.5 Zr _0.375 Y _0.125 O _1.9375 /0.5wt% Fe 34 44 - Example 3 Ce _0.4 Zr _0.45 Y _0.15 O _1.925 /0.4wt% Co 31 28 9.7 Example 4 Ce _0.2 Zr _0.6 Y _0.2 O _1.90 /0.7wt% Ni 17 17 0 Example 5 Ce _0.5 Zr _0.375 Y _0.125 O _1.9375 /1.0wt% Cu 29 27 6.9 Example 6 Ce _0.6 Zr _0.3 Y _0.1 O _1.95 /0.1wt% Rh 44 30 31.8 Example 7 Ce _0.4 Zr _0.45 Y _0.15 O _1.925 /0.1wt% Rh 35 30 14.3 Example 8 Ce _0.2 Zr _0.6 Y _0.2 O _1.9 /0.05wt% Rh 18 25 - Example 9 Ce _0.6 Zr _0.3 Y _0.1 O _1.95 /0.1wt% Pd 43 29 32.8 Example 10 Ce _0.4 Zr _0.45 Y _0.15 O _1.925 /0.05wt% Pd 33 27 18.2 Example 11 Ce _0.2 Zr _0.6 Y _0.2 O _1.9 /0.2wt% Pd 18 24 - Comparative Example 1 Ce _0.6 Zr _0.3 Y _0.1 O _1.95 22 11 50 Comparative Example 2 CeO ₂ 2 0 100 Comparative Example 3 Ce _0.6 Zr _0.3 Y _0.1 O _1.95 /0.1wt% Pt 44 30 31.8 Comparative Example 4 Ce _0.4 Zr _0.45 Y _0.15 O _1.925 /0.1wt% Pt 34 31 8.8 Comparative Example 5 Ce _0.2 Zr _0.6 Y _0.2 O _1.9 /0.1wt% Pt 18 20 -

Note: The unit of OSC in early and endurance is (1/1000) × (mo1O ₂ / mo1 oxide)

As is apparent from Table 1, the cerium-based composite oxides used in Examples 1 to 11 are much smaller than those of the cerium-based oxides used in Comparative Examples 1 and 2. In other words, the cerium-based composite oxide of the present invention, in other words, the cerium-based composite oxide in which the oxide of the rare earth metal is complexed, it is understood that even if the redox is repeated at high temperature, the oxygen storage function is maintained well. have.

In particular, it can be seen that the cerium-based composite oxides having the compositions of Examples 1 and 2 are excellent in any of an initial oxygen storage function, a durable oxygen storage function, and durability.

In addition, as can be seen from the comparison of Comparative Examples 3 to 5 and Examples 6 to 11, when the precious metal supported on the cerium-based composite oxide is rhodium or palladium instead of platinum, or when a transition element is contained, It can be seen that the oxygen streak function is maintained well even if the redox is repeated under the following conditions.

Therefore, the cerium-based composite oxide of the present invention can maintain the oxygen storage function well even when the redox is repeated at a high temperature of 1000 ° C. Because of the efficiency of the catalyst for purifying

Claims (9)

Represented by the general formula Ce _{1- (x + y)} Zr _x R _y O _2-z , R is a rare earth metal, Z represents the amount of oxygen bond, 0.2≤x + y≤0.9, 0.1≤x≤0.8, 0.05≤y≤0.3 oxygen absorption storage cerium-based composite oxide. The oxygen absorption storage cerium-based composite oxide according to claim 1, wherein in the general formula, 0.4 ≦ x + y ≦ 0.8, 0.35 ≦ x ≦ 0.7, and 0.05 ≦ y ≦ 0.2. The oxygen absorption storage cerium-based composite oxide according to claim 1 or 2, wherein the rare earth metal is Y. The oxygen-absorbing storage cerium-based composite oxide according to claim 1 or 2, wherein at least a part is a solid solution. The oxygen absorption storage cerium-based composite oxide according to claim 1 or 2, further comprising a noble metal. The oxygen absorption storage cerium-based composite oxide according to claim 5, wherein the noble metal is Pd or Rh. The oxygen absorption storage cerium-based composite oxide according to claim 1 or 2, wherein a transition element is supported. 8. The oxygen absorption storage cerium-based composite oxide according to claim 7, wherein the transition metal is at least one of a group consisting of Fe, Co, Ni, and Cu. 9. The oxygen absorption storage cerium-based composite oxide of claim 8, wherein the transition metal is Fe.